French President Francois Hollande (R) and German Chancellor Angela Merkel leave after delivering a joint statement after the European Union Summit of 27 Heads of State or Government in Bratislava, Slovakia on September 16, 2016. The 27 leaders -- minus British Prime Minister Theresa May -- gathered at Bratislava's towering castle overlooking the River Danube, determined to respond to the challenges of mass migration, security, globalisation and a stuttering economy. / AFP PHOTO / STEPHANE DE SAKUTINSTEPHANE DE SAKUTIN/AFP/Getty Images

Hungarian Prime Minister Viktor Orban delivers a speech during a business conference in Budapest, Hungary, March 10, 2016. REUTERS/Laszlo Balogh

French President Francois Hollande (C,R) and German Chancellor Angela Merkel leave after delivering a joint statement after the European Union Summit of 27 Heads of State or Government in Bratislava, Slovakia on September 16, 2016. The 27 leaders -- minus British Prime Minister Theresa May -- gathered at Bratislava's towering castle overlooking the River Danube, determined to respond to the challenges of mass migration, security, globalisation and a stuttering economy. / AFP PHOTO / STEPHANE DE SAKUTINSTEPHANE DE SAKUTIN/AFP/Getty Images

French President Francois Hollande (R) and German Chancellor Angela Merkel leave after delivering a joint statement after the European Union Summit of 27 Heads of State or Government in Bratislava, Slovakia on September 16, 2016. The 27 leaders -- minus British Prime Minister Theresa May -- gathered at Bratislava's towering castle overlooking the River Danube, determined to respond to the challenges of mass migration, security, globalisation and a stuttering economy. / AFP PHOTO / STEPHANE DE SAKUTINSTEPHANE DE SAKUTIN/AFP/Getty Images

French President Francois Hollande (R) and German Chancellor Angela Merkel leave after delivering a joint statement after the European Union Summit of 27 Heads of State or Government in Bratislava, Slovakia on September 16, 2016. The 27 leaders -- minus British Prime Minister Theresa May -- gathered at Bratislava's towering castle overlooking the River Danube, determined to respond to the challenges of mass migration, security, globalisation and a stuttering economy. / AFP PHOTO / STEPHANE DE SAKUTINSTEPHANE DE SAKUTIN/AFP/Getty Images

German Chancellor Angela Merkel adjusts a headphone as she delivers a joint statement with the French President after the European Union Summit of 27 Heads of State or Government in Bratislava, Slovakia on September 16, 2016. The 27 leaders -- minus British Prime Minister Theresa May -- gathered at Bratislava's towering castle overlooking the River Danube, determined to respond to the challenges of mass migration, security, globalisation and a stuttering economy. / AFP PHOTO / STEPHANE DE SAKUTINSTEPHANE DE SAKUTIN/AFP/Getty Images

French President Francois Hollande (L) and German Chancellor Angela Merkel deliver a joint statement after the European Union Summit of 27 Heads of State or Government in Bratislava, Slovakia on September 16, 2016. The 27 leaders -- minus British Prime Minister Theresa May -- gathered at Bratislava's towering castle overlooking the River Danube, determined to respond to the challenges of mass migration, security, globalisation and a stuttering economy. / AFP PHOTO / STEPHANE DE SAKUTINSTEPHANE DE SAKUTIN/AFP/Getty Images

French President Francois Hollande (L) and German Chancellor Angela Merkel deliver a joint statement after the European Union Summit of 27 Heads of State or Government in Bratislava, Slovakia on September 16, 2016. The 27 leaders -- minus British Prime Minister Theresa May -- gathered at Bratislava's towering castle overlooking the River Danube, determined to respond to the challenges of mass migration, security, globalisation and a stuttering economy. / AFP PHOTO / STEPHANE DE SAKUTINSTEPHANE DE SAKUTIN/AFP/Getty Images